(1) Field of the Invention
The present invention relates to a packet forwarding apparatus and a communication bandwidth control method and, more particularly, to a packet forwarding apparatus and a communication bandwidth control method suitable for communication quality assurance for packets transmitted over a network comprising a plurality of nodes.
(2) Description of Related Art
Improvement of computer-based communications environment is evolving. Internet Protocol (IP) that is used worldwide is a communication protocol for a network layer of the OSI reference model. According to the IP, IP addresses are assigned to the line interfaces of apparatuses as terminals and relay nodes and each apparatus is identified by an IP address. Normally, a network is set up for each autonomous system (AS) as a unit of management and, by interconnecting networks of management units, a broad worldwide network is configured.
Communication services that are available on infrastructures offered by carriers, namely, Internet Service Providers (ISPs) can be roughly divided into line provision service oriented to corporate users and ISP's connection service oriented to personal users. A major part of the line provision service for corporate users is shifting from the conventional service using leased lines such as, for example, Asynchronous Transfer Mode (ATM) networks and frame relay networks, to the service using Virtual Private Networks (VPNs) on IP networks, which is more advantageous in cost. On the other hand, as for the network connection service for personal users, with expanded bandwidth by the advance of Digital Subscriber Line (DSL) technology typified by Asymmetric Digital Subscriber Line (ADSL), both data transfer capacity and the quantity of users rise drastically. With the proliferation of Fiber to The Home (FTTH), the network environment is being developed to serve as a basis for the life of personal users.
For the above networking services for corporate and personal users, a packet forwarding service between user sites, for example, a user terminal to a user terminal or a user terminal to a server, goes mainstream. In a packet forwarding network, a packet forwarding technique termed tunneling is used. The tunneling means a mechanism of adding (encapsulation) another header called as an encapsulation header to a received IP packet and forwarding the packet based on information specified in the encapsulation header. The tunneling is a communications technique effective for an ISP network that provides a service using its infrastructure to transport a data packet received from an external network to another external network.
There is an expanding demand for transit network infrastructures that interconnect networks, such as a service of providing a Multi Protocol Label Switching (MPLS) network, which is called IP-VPN, a site-to-site packet delivery service using IP security (IPsec) provided to small and medium sites, and a remote access service. Wide Area Ethernet service which has lately attracted attention is a similar technique for data packet forwarding between a plurality of LANs.
To access an Internet network, a general user must subscribe to a provider (ISP) of network/line services and acquire a subscriber right to use a line. Normally, a user connects a terminal device at home to the network of the ISP to which the user subscribed and connection to another ISP's network or a corporate network is made via this network.
In general, an access network owned by an access line provider lies between a user terminal and the ISP to which the user subscribed. A node on the access network forwards data packets received from the user terminal to the ISP network by tunneling. As tunneling protocols, for example, Layer 2 Tunneling Protocol (L2TP), Virtual LAN (VLAN), IP security (IPsec), and Multi Protocol Label Switching (MPLS) can be used.
In IP networks, various kinds of multimedia data services are implemented. Traffic over IP networks is increasing year by year, particularly due to an increasing number of users of a file exchange service and a chat service by direct communication between terminals, which is called Peer to Peer (P2P), and large-volume content distribution like Video on Demand (VoD) coming into popular use. Also, there is an increasing demand for services requiring information transfer in real time, such as IP telephone service and TV conference service. In this situation, for example, traffic duration, the amount of transmission data changing with time, and the required quality of communication differ from one service to another. Consequently, if the above-mentioned diversified types of information are delivered across a single network, conventional communication control techniques that handle all data packets uniformly cannot accommodate the demands of services that users wish for.